shell> perl -de 'require "yourscript.pl"'

Loading DB routines from perl5db.pl version 1.22
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(-e:1):   require "yourscript.pl"
  DB<1> t
Trace = on
  DB<1> b Your::Class::new
  DB<2> c
  ...